Ecosystem Test

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Ecosystem Test - 82

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Weekly Quiz Competition

Question 1
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Choose the correct answers from the alternatives given .
Endergonic reactions

A
are always coupling reactions

B
can only occur if there is an input of energy

C
have products with less free energy than the reactants

D
all of the above are correct

Solution

Endergonic needs an input of energy to create the products, which have more free energy as a whole than the sum of free energy of each of the reactants. An example of this type of reaction in biology is photosynthesis. This process depends on the reaction to absorb energy in the form of sunshine from the surroundings for it to occur.
So, the correct option is 'can only occur if there is an input of energy'.
Question 2
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Choose the correct answers from the alternatives given .
Which of the following metabolic processes can occur without a net influx of energy from some other process ?

A
ADP $$^+$$ P $$\rightarrow$$ ATP $$^+$$ H2O

B
$$C_6$$$$H_{12}$$$$O_6$$ $$^+$$ $$6O_2$$ $$\rightarrow$$ $$6CO_2$$ $$^+$$ $$6H_2O$$

C
$$6CO_2$$ $$^+$$ $$6H_2O$$ $$\rightarrow$$ $$C_6$$$$H_{12}$$$$O_6$$ $$^+$$ $$6H_2O$$

D
$$CO_2$$ + $$2H_2O$$ $$\rightarrow$$ $$CH_4$$ $$^+$$ $$2O_2$$

Solution

C$$_6$$H$$_1$$$$_2$$O$$6$$ + 6O$$2$$ $$\rightarrow$$ 6CO$$2$$ +6H$$2$$O in this process glucose breaks down to give its hydrogens to the oxygen, it really does not need a lot of energy to begin and to keep going. It simply needs a small spark and then it can keep going until its done.
So, the correct option is 'C$$_6$$H$$_{12}$$O$$_6$$ + 6O$$_2$$ $$\rightarrow$$ 6CO$$_2$$ +6H$$_2$$O'
Question 3
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Quantities of mineral nutrients in soils of tropical rainforests are relatively low because

A
standing crop is small

B
microorganisms that recycle chemicals are not very abundant in tropical soils

C
decomposition of organic refuse and reassimilation of chemicals by primary productivity occur rapidly

D
nutrient cycles occur at a relatively slow rate in tropical soils

Solution

The high temperature and moisture of tropical rainforests cause dead organic matter in the soil to decompose more quickly than in other climates, thus releasing and losing its nutrients rapidly. The high volume of rain in tropical rainforests washes nutrients out of the soil more quickly than in other climates.
So, the correct option is 'decomposition of organic refuse and reassimilation of chemicals by primary productivity occur rapidly'.
Question 4
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Which of the following representations shows the pyramid of number in a forest ecosystem?

A

B

C

D
Solution
Correct Option: B
Explanation:
- The pyramid of numbers tends to represent the organism number across each trophic level.
- In a forest ecosystem, As the trophic level increase, the number of organisms decreases.
Hence, the pyramid of numbers is upright.
Question 5
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Mycorhhiza is an example of : -

A
Key-stone species

B
Endemic species

C
Critical link species

D
Rare species

Solution

A species whose presence and role within an ecosystem has a disproportionate effect on other organisms within the system. A keystone species is often a dominant predator whose removal allows a prey population to explode and often decreases overall diversity. It includes the American alligators, beavers, bees, elephants, gopher tortoises, grizzly bears, hummingbirds, ivory tree corals, jaguars, mountain lions, mycorrhizal fungi, Pacific salmon and prairie dogs. Thus, Mycorrhiza is a keystone species.
So the correct option is ' Key-stone species'.
Question 6
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Study the following statements and select the incorrect ones.
(i) Pyramids of energy and yearly biomass production can never be inverted, since this would violate the laws of thermodynamics.
(ii) Pyramids of standing crop and numbers can be inverted, since the number of organisms at a time does not indicate the amount of energy flowing through the system.
(iii) There are certain limitations of ecological pyramids such as they do not take into account the same species belonging to two or more trophic levels.
(iv) Saprophytes are not given any place in ecological pyramids even though they play a vital role in the ecosystem.

A
(i) and (ii)

B
(iii) and (iv)

C
(ii) and (iii)

D
None of these

Solution

The second law of thermodynamics states that whenever energy is transformed, there is a loss energy through the release of heat. This occurs when energy is transferred between trophic levels as illustrated in a food web. When one animal feeds off another, there is a loss of heat (energy) in the process. Additional loss of energy occurs during respiration and movement. Hence, more and more energy is lost as one moves up through trophic levels. If this pyramid is inverterved, it would violate the law of thermodynamics. Hence the pyramid can never be inverted.
The pyramid of numbers depicts the relationship in terms of the number of producers, herbivores and the carnivores at their successive trophic levels. There is a decrease in the number of individuals from the lower to the higher trophic levels. The number pyramid varies from ecosystem to ecosystem. Since the amount if energy flowing through the system is not indicated, the pyramid can be inverted.
These are the diagrammatic illustrations of connection between different trophic levels in terms of energy, biomass and number of an organism. The base of each pyramid represents the producers or the first trophic level. Apex represents tertiary or top level consumers. If any species belongs to two or more trophic level, it can causes differences and issues in energy flow and numbers.
Saprophytes are organisms which feed on dead and decaying matter and these pyramid exhibit interaction between the living components and decomposers interact with dead organisms at all level. This makes it difficult to place it in the ecological pyramid. Hence, they are not given any place in ecological pyramids even though they play a vital role in the ecosystem.
So the correct option is 'none of these'.
Question 7
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The species of plants that play a vital role in controlling the relative abundance of other species in a community are called

A
edge species

B
keystone species

C
pioneer species

D
seral species.

Solution

A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity. It became a popular concept in conservation biology, alongside flagship and umbrella species. Although the concept is valued as a descriptor for particularly strong inter-species interactions, and it has allowed easier communication between ecologists and conservation policy-makers, it has been criticized for oversimplifying complex ecological systems.
So the correct option is 'keystone species'.
Question 8
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In order to estimate the gross primary productivity (GPP) of a pond containing phytoplankton and zooplankton, a student collected water samples from the pond in two bottles labelled X and Y. The dissolved oxygen (DO) of the samples immediately after collection was $$8$$mg $$ml^{-1}$$. The DO content when measured after $$24$$ hours of incubation was as follows:
Bottle X: $$2$$ mg $$ml^{-1}$$ after incubation in dark
Bottle Y: $$18$$ mg $$ml^{-1}$$ after incubation in light
GPP of the pond is?

A
$$6$$

B
$$10$$

C
$$16$$

D
$$20$$

Solution

GPP or Gross Primary productivity is referred as the total rate of photosynthesis including the organic matter used up in respiration during the measurement period.
When the bottles X and Y containing pond water are kept in dark and light respectively, there is decline in Dissolved oxygen (DO) in bottle X because phytoplankton and zooplankton will not be able to photosynthesise and the oxygen will be used up in respiration whereas, there is increase in DO in bottle Y because phytoplankton and zooplankton will photosynthesise in presence of light resulting in production of oxygen.
So, from the information given,
Respiratory activity can be calculated as : Initial DO - DO after incubation in dark = 8 - 2= 6 mg/ml
Net photosynthetic activity can be calculated as : DO after incubation in light - Initial DO = 18 - 8= 10 mg/ml
GPP = Net photosynthetic activity + Respiratory activity = 10 + 6 = 16.
So, the correct answer is C.
Question 9
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In an open ocean, the biomass of primary producers (microscope algae) is often lower than the biomass of higher trophic levels (zooplankton and fish), as illustrated by an inverted pyramid of biomass. How can there be enough food in an open ocean to support the higher trophic levels?

A
The microscopic primary producers are a source of food of high quality

B
The microscopic primary producers have high rates of growth and reproduction

C
The microscopic primary producers are less abundant

D
The higher tropic levels are cold-blooded animals which do not require much food.

Solution

In an open ocean, the large numbers of phytoplankton quickly complete their life cycles and sets of new population or crops of phytoplankton are formed every few hours or fays. Thus, the cumulative energy contents that these generation after generation of phytoplankton trap in course of a year is certainly much more than trapped by only a few generations of herbivorous fishes in the corresponding time and space.
Question 10
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The given pyramid best represents

A
Pyramid of energy in forest ecosystem

B
Pyramid of biomass in forest ecosystem

C
Pyramid of numbers in grassland ecosystem

D
Pyramid of numbers in forest ecosystem
Solution
Correct option: D

Explanation:
- The given pyramid best represents Pyramid of numbers in forest ecosystem.
- The given pyramid best represents pyramid of numbers in forest ecosystem as it is spindle-shaped. The producers are giant size trees in the forest ecosystem, and they form the base of the pyramid. The producers are usually less in number, but they support a higher number of herbivores such as deer, birds and elephants. The number goes down at each succeeding level as the primary consumers support very fewer numbers of carnivores. This results in a spindle-shaped structure of the pyramid of numbers in the forest ecosystem.
- Thus, Option D is correct.